Please help! How do I sort my metabolism out?

fiendette

Hi guys,
I need a little help and advice...
Last year I was very ill for around 3 months and I hardly ate anything in that time period... I was borderline anorexic and I was eating 600 calories or even less a day. As you can imagine, I lost a ton of weight and once I got better I started eating normally again, I put all the weight back on and much more. I am now a stone over the weight I was before I got ill, and I'd really like to go back to how I was!
Trouble is, I'm worried that this has royally screwed up my metabolism. I have noticed that I'm only losing weight if I am eating around 1,200 calories a day and exercising, but I recently calculated my daily calorie needs using my BMR and so I upped my calorie intake for 2 weeks. I still exercised 3-4 days a week and ate healthily, but I put on weight. I'm not really sure what to do as I'm not overeating and generally now I'm eating around 1,600 calories a day but I'm putting on weight? My daily calorie needs are around 1886 calories. (I am 22, female, 5'11 and 11 stone 4)
Any help would be appreciated, as I'm not sure what I am doing wrong?
Thanks